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<title>Using as: s390 Options</title>

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<a name="s390-Options"></a>
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<p>
Next: <a href="s390-Characters.html#s390-Characters" accesskey="n" rel="next">s390 Characters</a>, Up: <a href="S_002f390_002dDependent.html#S_002f390_002dDependent" accesskey="u" rel="up">S/390-Dependent</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Options-19"></a>
<h4 class="subsection">9.38.1 Options</h4>
<a name="index-options-for-s390"></a>
<a name="index-s390-options"></a>

<p>The following table lists all available s390 specific options:
</p>
<dl compact="compact">
<dd><a name="index-_002dm31-option_002c-s390"></a>
<a name="index-_002dm64-option_002c-s390"></a>
</dd>
<dt><code>-m31 | -m64</code></dt>
<dd><p>Select 31- or 64-bit ABI implying a word size of 32- or 64-bit.
</p>
<p>These options are only available with the ELF object file format, and
require that the necessary BFD support has been included (on a 31-bit
platform you must add &ndash;enable-64-bit-bfd on the call to the configure
script to enable 64-bit usage and use s390x as target platform).
</p>
<a name="index-_002dmesa-option_002c-s390"></a>
<a name="index-_002dmzarch-option_002c-s390"></a>
</dd>
<dt><code>-mesa | -mzarch</code></dt>
<dd><p>Select the architecture mode, either the Enterprise System Architecture
(esa) mode or the z/Architecture mode (zarch).
</p>
<p>The 64-bit instructions are only available with the z/Architecture mode.
The combination of &lsquo;<samp>-m64</samp>&rsquo; and &lsquo;<samp>-mesa</samp>&rsquo; results in a warning
message.
</p>
<a name="index-_002dmarch_003d-option_002c-s390"></a>
</dd>
<dt><code>-march=<var>CPU</var></code></dt>
<dd><p>This option specifies the target processor. The following processor names
are recognized:
<code>g5</code>,
<code>g6</code>,
<code>z900</code>,
<code>z990</code>,
<code>z9-109</code>,
<code>z9-ec</code>,
<code>z10</code>,
<code>z196</code>,
<code>zEC12</code>, and
<code>z13</code>.
Assembling an instruction that is not supported on the target processor
results in an error message. Do not specify <code>g5</code> or <code>g6</code>
with &lsquo;<samp>-mzarch</samp>&rsquo;.
</p>
<a name="index-_002dmregnames-option_002c-s390"></a>
</dd>
<dt><code>-mregnames</code></dt>
<dd><p>Allow symbolic names for registers.
</p>
<a name="index-_002dmno_002dregnames-option_002c-s390"></a>
</dd>
<dt><code>-mno-regnames</code></dt>
<dd><p>Do not allow symbolic names for registers.
</p>
<a name="index-_002dmwarn_002dareg_002dzero-option_002c-s390"></a>
</dd>
<dt><code>-mwarn-areg-zero</code></dt>
<dd><p>Warn whenever the operand for a base or index register has been specified
but evaluates to zero. This can indicate the misuse of general purpose
register 0 as an address register.
</p>
</dd>
</dl>




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